PHOSPHORIC INSECTS. 141 



assert without danger, that in gases which extin- 

 guish combustion the luminous substance ex- 

 tracted from glowworms shines for thirty or forty 

 minutes. 



The same author next remarks, that in oxygen 

 gas, the phosphorescence of the luminous sub- 

 stance shines three times longer. Only three times. 

 But this may be due to a diiference of vitality 

 in the different individual insects submitted to 

 examination. Heat increases the light of glow- 

 worms ; too great a temperature destroys it. 



On the whole, the experiments of M. Matteucci, 

 made with remarkable delicacy, can lead to no 

 conclusion which tends to establish the nature of 

 the phosphorescence of the Lampyrida ; unless, 

 indeed, this conclusion be that the phenomenon 

 in question is not directly owing to combustion. 



With the exception of a single one, the same 

 may be said of those undertaken by M. Roberts, 

 and communicated to the ' Annales des Sciences 

 Naturelles' in December, 1842. M. Roberts has, 

 however, noted a fact similar to the observation 

 of Mr. Macartney, regarding the luminous sub- 

 stance of the Scolopendra. I shall give it in his 

 own words : 



" If a female Lampyris be divided into two 

 transversal halves, the light spread around by the 

 abdominal portion disappears in about half an 

 hour. But by placing this same portion near a 



